I have a 67 Camaro with a 11 inch brake booster. I run a vacume canister on this. I'd like to switch to a 9 inch booster without having to run a vacume pump.

Will it work?

If the 9" booster is a dual diaphram.. You should get away with it..

Scroll down this page.. There are sevaral dual diaphram boosters listed.
http://www.mbmbrakeboosters.com/brakebooster.html
A PB9521 would look at home and reasonably OE with the gold/green zinc.